Issues #637 "Add metric description" implementation

[aivanov-oneinc]

Suggestion to resolve #637

Details on the issue fix or feature implementation

I saw in the protobuf contracts for Prometheus the help field exists and is even written to the output, but in the Options classes for all metrics it is absent. So I decided that I can add the "Description" property to the Options and init its value with Options of the appropriate metric.

Also, I've added unit tests that check how the output formatting looks.

Also, I've fixed the small issues with the Prometheus sandbox app

Confirm the following

• I have ensured that I have merged the latest changes from the dev branch
• I have successfully run a local build
• I have included unit tests for the issue/feature
• I have included the github issue number in my commits